Diabetes is a worldwide public health problem. Veterans are disproportionally impacted by diabetes compared to the general population. Diabetes exacts a heavy toll on veterans, doubling their risk of death. The majority of hospitalizations and deaths in veterans with diabetes are due to vascular complications such as myocardial infarctions and strokes. Diabetes leads to these complications because it promotes dysfunction of the vascular endothelium and accelerates atherosclerosis. Oxidative stress has many deleterious effects on blood vessel function and is a prominent feature of the diabetic vasculature. P66shc is a protein expressed in diabetic blood vessels where it stimulates oxidative stress. P66shc is a major factor responsible for diabetic vascular dysfunction and accelerated atherosclerosis. How p66shc is regulated in diabetic blood vessels is not known. The immediate goal of this application is to understand the fundamental mechanism governing p66shc function in diabetic blood vessels, with the eventual goal of leveraging this knowledge to prevent and treat diabetic vascular disease. This application will explore a novel relationship between p66shc and the SIRTUIN1 (SIRT1) lysine deacetylase in the diabetic vascular endothelium. It centers on the novel hypothesis that endothelial p66shc is lysine acetylated in diabetes, that lysine acetylation activates p66shc, that lysine acetylated p66shc plays an indispensable role in leading to diabetic vascular dysfunction and accelerated atherosclerosis, and SIRT1 ameliorates diabetic vascular disease by directly deacetylating endothelial p66shc. Studies proposed in this application will ask 1) how lysine acetylation by diabetes activates p66shc at the molecular level, thus promoting oxidative stress in the vascular endothelium, and 2) whether diabetic vascular dysfunction and disease can be prevented or retarded if p66shc cannot be acetylated. It will address these points by using unique molecular tools including mice lacking endothelial SIRT1 and mice in which endothelial p66shc is not acetylatable. Why investigate this novel relationship between SIRT1 and p66shc? Current therapies to treat or prevent diabetic vascular disease and its attendant complications, including heart attacks and strokes, are woefully inadequate. Even reducing blood sugar has proven largely ineffective in preventing atherosclerotic complications of diabetics. Add to this that there are several pharmaceuticals that have been developed as activators of SIRT1 and are safe when given to humans. If studies in this application prove that SIRT1 plays a major beneficial role in preventing vascular dysfunction and accelerated atherosclerosis of diabetes by deacetylating p66shc, these SIRT1 activators could find a new use in the treatment of diabetic vascular disease. In addition, showing that lysine acetylation of p66shc is the principal mechanism responsible for diabetic vascular disease could open the door for developing pharmaceuticals that target this acetylation pathway as novel therapies for diabetic vascular complications.